This invention relates to a level and/or angle finder. For purposes of illustration in this application, two separate but closely related embodiments are disclosed. Except where necessary to distinguish between these two embodiments, the term "angle finder" will be used for convenience.
The angle finder is used to determine any angle when a "leg" is not present which corresponds to the gravitational levelness of the earth. In describing the invention in this application, the term "gravitational vector" will be used to describe a gravitational force in a straight-line direction which would usually correspond to the gravitational pull of the earth but would also include instances where the apparatus is being used in areas of artificial gravity.
Prior art devices relating to this invention include the McInerney U.S. Pat. No. 4,253,242. This patent describes a digital angle indicator which includes a gravity responsive rotor with four arc slots machined through the rotor. The McInerney patent measures the position of a reference surface relative to eight predetermined angles forty-five degrees apart. Photodetectors act as shutters and a hard wired circuit computes the position of the device relative to one of the predetermined eight angles. In the disclosure of the McInerney patent, the user does not know the degree of error but only whether the angular position of the angle indicatorr is greater or less than one of the predetermined angles. McInerney also discloses a number of variations, including the use of a transparent rotor and the use of rotors with varying sized slots to vary the amount of angular deviation which is permitted from a nominal desired position.
However, while the McInerney patent is referred to as a "digital" angle indicator, in fact the term "binary" should be used to refer to the fact that a visual indication shows only whether the surface under inspection has or does not have the desired angular alignment. It does not provide a readout of the actual angle of the surface under inspection.